Hydroentangled nonwoven fabric and method of producing the same

ABSTRACT

A reinforced hydroentangled nonwoven fabric having small thickness and weight, draping characteristics and flexibility, and improved balance of longitudinal and transverse strength, and more particularly a thin, light-weight, reinforced, hydroentangled nonwoven fabric (9) obtained by entangling the fiber of a reinforcing support base (2) or the fiber of a fiber web laminated on the fiber of the support base (2) with the support base (2) and uniting them by ejecting high-pressure thin water jet streams (5a, 5b) against these materials, characterized in that the reinforcing support base (2) comprises a stretched unidirectionally oriented nonwoven fabric obtained by stretching a nonwoven fabric of long fiber, which is produced by spinning a thermoplastic resin, in the direction with the fiber oriented substantially in one direction, or stretched, crossed, laminated, nonwoven fabric obtained by cross-laminating the stretched unidirectionally oriented nonwoven fabric; and a method of producing the same.

FIELD OF THE INVENTION

The present invention relates to an improved hydroentangled nonwovenfabric and a method of producing the same. More particularly, theinvention relates to a thin and lightweight hydroentangled nonwovenfabric, which is suitable for use in various purposes because it hasgood lint-free property (free from fluffiness) and improved drapeproperty (cover and well fit to an outer shape). In addition, thenonwoven fabric of the invention has the smoothness and soft texturelike those of ordinary cloths and the strength in longitudinal andtransverse directions (warp and weft) are balanced.

The method for producing nonwoven fabrics according to the presentinvention can be carried out easily and rapidly with retaining the highproductivity inherent in the web forming process and hydroentanglingprocess (water jet intertwining process).

Moreover, the present invention relates to a thin, lightweight andreinforced hydroentangled nonwoven fabric, which can be widely used asclothing materials such as interlinings, industrial materials such asfilters and wipers and disposable medical products such as surgicalgowns, bed-sheets, towels and face masks and to the method of producingthe same.

BACKGROUND ART

The prior art hydroentangling method involves the process to subject acard web to high pressure fluid jet streams in order to entangle fibersin web and thereby providing specific entangled structure and suitablemechanical properties to the web.

The nonwoven fabrics produced by this hydroentangling process permitshigher mobility of fibers within the fabrics than any other textilefabrics and nonwoven fabrics because the fibers are simply mechanicallyentangled and not firmly bonded together. Therefore, they have soft andlint-free properties together with improved drape and soft touchproperties. On the other hand, they possess disadvantages that they lackmechanical strength and dimensional stability due to the absence of firmfiber bonding.

Furthermore, they also possess another disadvantage that theirmechanical strengths in the longitudinal and transverse directions arenot balanced because continuous lines are formed in the web in themachine direction by the jet streams of high pressure fluid in themanufacturing process. The imbalance of this kind in mechanical strengthmay be avoided by applying cross-layer process. However, thecrossing-over the web and/or laminating process unfavorably brings aboutthe thickening of resultant nonwoven fabrics and adversely affects theproductivity.

In order to solve these problems, various methods have been proposed.Japanese Patent Laid-Open Publication No. 54-82481 discloses a use ofnonwoven fabrics made of staple fibers as a reinforcing base material.Japanese Patent Laid-Open Publication No. 54-101981 and No. 61-225361disclose the use of woven or knitted fabric or nonwoven fabric as areinforcing material. Japanese Patent Laid-Open Publication No. 59-94659discloses the use of wood pulp as a reinforcing base material. JapanesePatent Laid-Open Publication No. 01-321960 and No. 04-263660 disclose aprocess of entangling card web with a reticular base material. JapanesePatent Laid-Open Publication No. 04-333652 and No. 04-153351 disclose aprocess of entangling card web with spun-bonded nonwoven fabric.

With these prior art techniques, although it is possible to improve themechanical strength of hydroentangled nonwoven fabrics made, it is notpossible to produce, in an economical and simple manner, a thin,lightweight nonwoven fabric having improved balance in strength whileretaining its properties such as softness, lint-freeness, drape propertyand soft touch feeling which are the characteristics of hydroentanglednonwoven fabric.

The incorporation of a cross-layer process in order to improve thebalance in mechanical strength of a nonwoven fabric usually brings aboutthe lowering of productivity in the web formation process to a level of1/2 to 1/5. In addition, the productivity of subsequent hydroentanglingprocess is also lowered. Even when similar process is done duringhydroentangling process or in the subsequent process, similarly, it isnot possible to avoid the reduction of productivity. As described above,however, it is apparent that there has not been established any suitabletechnology to produce a hydroentangled nonwoven fabric having improvedproperties together with balanced longitudinal and transverse strengthswithout sacrificing the inherent high productivity of the web formationand hydroentangling processes.

DISCLOSURE OF THE INVENTION

As a result of the intensive studies to solve above-described problems,the finding made by the inventors of this application is that a thin andlightweight hydroentangled nonwoven fabric having improved drape andtextile-like characteristics, particularly with excellent lint-freenessand the balance in longitudinal and transverse strengths can beproduced. This can be attained through the process that at least onelayer of long fiber nonwoven fabric is stretched or rolled so as toarrange its fibers in one direction or a multi-layer material containingthe same is then subjected to high pressure water jet streams toentangle the long fibers.

It is, therefore, a first aspect of this invention relates to theprovision of a hydroentangled nonwoven fabric which is characterized inthe steps that a long fiber nonwoven fabric spun from a thermoplasticresin is unidirectionally stretched to arrange its fibers almost in onedirection so as to obtain a stretched unidirectionally arranged nonwovenfabric and at least one of the thus obtained nonwoven fabric or across-laid down and/or laminated nonwoven fabric made of the abovenonwoven fabrics is subjected to high pressure water jet streams toentangle the fibers of nonwoven fabric.

A second aspect of this invention relates to the provision of ahydroentangled nonwoven fabric which is characterized in that a suitablefiber web is put in layers with the above stretched unidirectionallyarranged nonwoven fabric or the stretched cross-laid down and/orlaminated nonwoven fabric and the fibers in multi-layer material isentangled by high pressure water jet streams.

A third aspect of the present invention relates to the provision of ahydroentangled nonwoven fabric which is made by using a stretchedunidirectionally arranged nonwoven fabric or stretched cross-laid downand/or laminated nonwoven fabric and the card web made of staple fiberssuch as natural, regenerated or synthetic staple fibers and byentangling the material with high pressure water jet streams.

A fourth aspect of this invention relates to the provision of ahydroentangled nonwoven fabric which is united into one body byentangling, using high pressure water jet streams, the stretchedunidirectionally arranged nonwoven fabric or the stretched cross-laiddown and/or laminated nonwoven fabric and a long fiber web, in which anunstretched long fiber nonwoven fabric prior to the stretchingtreatment, a stretched randomly arranged nonwoven fabric, anon-stretched random or unidirectionally arranged nonwoven fabric or afiber web consisting of natural staples, regenerated staples orsynthetic long fibers are used.

A fifth aspect of the present invention relates to the provision of ahydroentangled nonwoven fabric characterized in that the stretchingratio of the stretched unidirectionally arranged nonwoven fabric is 5 to20, the average fineness is 0.01 to 10 denier and its basis weight is 1to 80 g/m².

Furthermore, a sixth aspect of the invention relates to the provision ofa method for the preparation of a hydroentangled nonwoven fabric, whichmethod is characterized in that the entangling treatment by applyinghigh pressure water jet streams is done at a water pressure of 10 to 300kg/cm² toward the stretched unidirectionally arranged nonwoven fabric,stretched cross-laid down nonwoven fabric or their laminates with asuitable fiber web, and the processing speed is made in the range of 2to 200 m/min.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic flow sheet illustrating an example of the processof the method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail in the following.

The above-described long fiber nonwoven fabric can be formed by variousknown methods. As a characteristics of the nonwoven fabric, it isrequired that fibers are distributed uniformly not only within the planebut also in the direction of thickness of the nonwoven fabric and thatthe fibers are arranged regularly in a certain direction. The longfibers used for the formation of a nonwoven fabric may be previouslystretched ones, however, they must be still stretchable more than twicein length in subsequent stretching operation.

There have bene proposed various methods for the formation of a longfiber nonwoven fabrics.

(1) A process to provide rotating or vibrating action to filaments spunfrom thermoplastic resins using hot air and thereby providing fiberarrangement in the longitudinal direction or transverse direction toform a nonwoven fabric, in which most of the fibers are unidirectionallyarranged.

(2) A process of spinning of a thermoplastic resin followed by drawing,stretching, opening, collecting and thermal point bonding to form anonwoven fabric, e.g. spunbonded process.

(3) A process of spinning a thermoplastic resin with high pressure andhigh temperature air followed by opening the obtained long fibers andarranging them to form a nonwoven fabric, e.g. melt-blown process.

(4) A process of stretching and crimping bundles of long fibers spunfrom a thermoplastic resin followed by opening and spreading them toform a nonwoven fabric, e.g. tow opening process.

(5) A process of expansion extrusion of a thermoplastic resin followedby foam bursting, laminating and extension to form a nonwoven fabric,e.g. burst fiber process.

As described above, according to the present invention, the highpressure hydroentangling is carried out using a stretchedunidirectionally arranged nonwoven fabric comprising at least one layerof nonwoven fabric which is made by unidirectionally stretching the longfibers spun from a thermoplastic resin and arranged in one direction, ora stretched cross-laid down and/or laminated nonwoven fabric formed byoverlaying with each other the above-mentioned stretchedunidirectionally arranged nonwoven fabrics in such a manner that theaxial directions of the arranged fibers of them are crossed.

The term "stretching" as used herein may refer to not only various typesof stretching operation but also the rolling operation which is able toachieve similar effect as stretching operation. That is, variousconventionally employed stretching methods utilized for the productionof films and nonwoven fabrics such as longitudinal stretching,transverse stretching and biaxial stretching may be employed.

As the longitudinal stretching method, short distance roll stretchingmethod is preferable because it enables the stretching withoutdecreasing the width of material. In addition, a stretching method suchas rolling, hot air stretching, hot water stretching and steamstretching may be useful.

As a transverse stretching method, although the tenter method used ofthe biaxial stretching of films may be used, the pulley type transversestretching method as disclosed in the aforementioned Japanese PatentPublication No. 03-36948 and the transverse stretching method by meansof combined grooved rolls (grooved roll method) can be used because oftheir simple operation.

As a biaxial stretching method, a tenter-type simultaneouslybiaxial-stretching method which is used for the biaxial stretching offilms can be employed. However, it is also possible to accomplish thebiaxial stretching by combining the above-described longitudinalstretching and the transverse stretching operation.

The draw (stretching) ratio of the above-described stretchedunidirectionally arranged nonwoven fabrics is 5 to 20, preferably 8 to12. The average fineness of the stretched nonwoven fabric is in therange of 0.01 to 10 denier, preferably 0.03 to 5. The basis weight ofsingle layer or laminated nonwoven fabric is in the range of 1 to 80g/m², preferably 5 to 30 g/m².

According to the present invention, the high pressure hydroentanglingcan be carried out using any suitable fiber web or nonwoven fabrictogether with the aforementioned stretched unidirectionally arrangednonwoven fabrics or the stretched cross-laid down and/or laminatednonwoven fabric formed by laminating the stretched unidirectionallyarranged nonwoven fabrics. The above fiber web includes card webs andlong fiber webs of synthetic fiber, both of which are composed ofnatural staples, regenerated staples or synthetic staples, a long fibernonwoven fabric which is the material before the stretching of thestretched unidirectionally arranged nonwoven fabric, a stretchedrandomly arranged nonwoven fabric, and a non-stretched randomly orunidirectionally arranged nonwoven fabric.

As the thermoplastic resins which can be used as the raw materials ofthe long fiber nonwoven fabrics in accordance with the presentinvention, there are exemplified by high density, intermediate densityor low density polyethylene, linear low density polyethylene, ultra lowdensity polyethylene, propylene based polymers such as polypropylene andpropylene-ethylene copolymers, α-olefin polymers, polyamides,polyesters, polycarbonates, and polyvinyl alcohols. Among them,polypropylene and polyesters are particularly preferably.

These polymers may be used with the addition of anti-oxidants, UVabsorbers, lubricants or the like.

The nonwoven fabric to be used for the high pressure hydroentangling inaccordance with the present invention can be any one if it contains atleast one layer of the aforementioned stretched unidirectionallyarranged nonwoven fabrics which was subjected to unidirectionallystretching and unidirectional orientation in the fiber arrangement.Further, it is possible to combine the stretched unidirectionallyarranged nonwoven fabrics with the same type or different type ofstretched unidirectionally arranged nonwoven fabrics, or another fiberweb or nonwoven fabrics. It is preferably that two or more layers arecombined. When the nonwoven fabric comprises two or more layers ofstretched or oriented nonwoven fabrics, their directions of stretchingor fiber arrangement can be either the same or in crosswise with eachother.

The card webs made of natural or regenerated staples and the long fiberwebs made of synthetic staples to be used in the present invention cabbe formed using any of the following fibers or a mixture of them as rawmaterials. For example, natural fibers such as cotton, liter and pulp,regenerated cellulose fibers such as rayon and cupra, semi-syntheticcellulose fibers such as acetate fibers, synthetic fibers such aspolyethylene, polypropylene, polyester, polyamide, polyacrylonitrile andpolyvinyl alcohol fibers, polyurethane or polyester based elastomerfibers, conjugate fibers and composite ultra-fine fibers which are madeby dividing or splitting by means of high pressure water jet streams.Furthermore, as a long fiber web, the long fiber nonwoven fabric priorto the stretching for preparing the stretched unidirectionally arrangednonwoven fabric, a stretched randomly arranged nonwoven fabric, anon-stretched randomly or unidirectionally arranged nonwoven fabric areincluded.

In order to form the fiber web, several processes are employed such as aprocess to cut wet-spun regenerated fibers or synthetic fibers melt-spunby an ordinary method followed by disentangling the fibers into web by acarding machine, a process to disentangle natural fibers into web by acarding machine or a process to chop and split natural fibers and toform a web by paper-making procedure.

The fineness of the fiber of the card web is preferably in the range of0.01 to 15 denier, more preferably, 0.03 to 5 denier and its length ispreferably in the range of 1 to 100 mm, more preferably, 10 to 60 mm. Ifthe fineness of a single fiber is less than 0.01 denier, nonwoven fabricwith inferior lint-freeness will be resulted. If the fiber fineness isover 15 denier, touch feeling of the nonwoven fabric will be harsh. Ifthe fiber length is smaller than 1 mm, the mechanical strength ofnonwoven fabric is low due to insufficient fiber entangling. If thefiber length is more than 100 mm, the dispersion of fibers is not good.

The basis weight of the fiber web is preferably in the range of 10 to150 g/m², more preferably, 20 to 50 g/m². If it is less than 10 g/m²,the density of fibers is uneven for the high pressure water jet treatingprocess. When it is over 150 g/m², the nonwoven fabric is inferior inview of small thickness and lightweight property.

Accordingly, in this invention, as the combination of theabove-described card web with the stretched unidirectionally arrangednonwoven fabric or stretch cross-laid down and/or laminated nonwovenfabric (hereinafter referred to as "reinforcing support base"),laminates of two or more layers can be used, which are made byoverlaying alternately the card webs (A) with the reinforcing supportingbases (B). The combinations are exemplified by those having layerstructure of A/B, A/B/A, B/A/B, and A/B/A/B.

In the following, the method for producing the hydroentangled nonwovenfabric of the present invention will be described.

The producing process of the present invention includes:

(1) Forming processes for a card web and a reinforcing support base.

(2) Laminating and feeding process in which a card web is overlaid witha reinforcing support base and it is fed to the next process.

(3) High pressure hydroentangling process in which water jet treatmentis carried out.

(4) Drying process, and

(5) Product takeup process.

In the card web forming process, various methods and various patterns offiber arrangement may be adopted depending on the raw materials used andthe uses of final products. As a characteristic features of the cardweb, uniform fiber distribution within the machine direction (MD) andcross direction (CD) of the card web as well as in the verticaldirection of (ZD) is required.

The following examples are methods to provide various patterns of fiberarrangement in the card web.

(1) Card-parallel system by means of a mechanical card web formationmethod in which fibers are two-dimensionally (MD & ZD) arranged in thelongitudinal direction.

(2) Semi-random system wherein a semi-random apparatus provides anintermediate fiber arrangement between two dimensions (MD & CD) andthree dimensions (MD, CD & ZD).

(3) Random system wherein fibers are blown off by air blower and fibersare collected on screen meshes.

(4) Spunbond system in which continuous web formation is done byspinning a synthetic resin in wet or dry method, which is followed bystretching, fiber opening, collecting and entangling.

(5) Wet web formation system wherein natural fibers or regeneratedfibers are chopped and a web is formed through paper-making process.

In addition, even though the productivity is reduced to some extent, acard-cross layer system can be used as a method to improve the balanceof mechanical strengths in three directions by means of mechanical crossweb formation method in which fibers are crosswise arranged in obliquedirections.

FIG. 1 is a schematic illustration of an example for steps of layingand/or laminating-supplying step and subsequent steps.

In the supplying step, fiber webs 1 and a reinforcing support base 2 aresupplied from unwinding rolls 1a and 2a, respectively, depending on thelayer structure of the product to be produced. This step is carried outin off-machine, however, it is also possible to carry out this step inon-machine system, in which the fiber webs and the reinforcing supportbase are overlaid in a fiber collecting section of fiber web formationprocesses and the obtained laminate is delivered continuously to thesubsequent high pressure hydroentangling process.

In the next high pressure hydroentangling process, a large number offine water jet streams 5a are applied from the rows of small diameternozzles 5 toward the laminate 4 comprising fiber webs 1 and areinforcing supporting base 2 supplied on a roll or a screen whichserves as a water permeable or impermeable supporting member 3. In orderto improve process efficiency, it is preferable to wet the laminate 4previously by immersing it into water 6a in an immersion apparatus 6before subjecting it to the water jet streams and to remove water fromthe laminate using a water suction apparatus 7 equipped with a vacuummeans or the like after the water jet stream treatment.

Further, it is desirable to apply the high pressure hydroentangling toboth sides of the web laminate in order to achieve effectivehydroentangling. That is, the laminate 4 delivered from the firstsupporting member 3 is guided on the second supporting member 3a byreversing it and the hydroentangling is again carried out by applyingfine water jet streams 5c from the rows of small diameter high pressurewater jet nozzles 5c on the reverse side of the laminate, whichlaminated has already been subjected to the entangling treatment bywater jet streams 5a.

In the high pressure hydroentangling process, when the high pressurewater jet treatment is carried out on the screen, there is not anyparticular requirement for the screen to be used, however, it ispreferable to select adequate quality of material, mesh size and wirediameter taking in order to facilitate the discharging of process water.The mesh size of the screen is usually ranges from about 20 to 200 mesh.

In the high pressure water jet treatment wherein a water permeablesupporting member is used, the process water can be discharged withoutdifficulty. Therefore, the damaging of uniformity in product due topossible web scattering caused by the water jet streams can be avoided.However, the energy efficiency may not be high because the process wateronce passed through the laminate web still holds considerably amount ofenergy.

On the other hand, in the high pressure water jet treatment whereinwater impermeable supporting member is used, water jet streams oncepassed through the laminate web collide against the supporting member togenerate repulsed water jet streams, thereby providing entangling actionagain to the laminate. Thus, an improved entangling efficiency will beexpected owing to the interaction between jetted stream and repulsedstream of jets. However, it generates a disadvantage of the lowering ofentangling stability because the entangling is carried out by jettinghigh pressure water jet streams to the laminate web which is floating inwater.

As a result, it is preferable to perform the high pressure water jettreatment on a water permeable supporting member.

The streams of water jet are ejected from the rows of small diameternozzles arranged in a pitch of 0.2 mm or more from the verticaldirection relative to the direction of laminate movement. The diameterof orifices of the small diameter nozzles is usually less than 1 mm andpreferably, in the range of 0.1 to 0.5 mm. The liquid to be jetted ispreferably water, but hot water or ultra pure water may be used whenhygienic consideration is needed. The pressure of the water jet streamsranges from 10 to 300 kg/cm², preferably, 20 to 200 kg/cm². When thepressure of water jet stream is lower than 10 kg/cm², any sufficiententangling effect may not be expected. Meanwhile, when it is higher than300 kg/cm², the increase in the cost for high pressure water jet streamand difficult in handling may be brought about, so that both the casesare undesirable.

The entangling process by jetting high pressure water is usuallyconducted more than once. It is preferable to carry out the entanglingprocess using a plurality of rows of nozzles and jetting high pressurewater with increasing the pressure step by step. That is, the rows ofnozzles in the first stage eject relatively low pressure water streamsto entangle the surface layer of the laminate web, and subsequent rowsof nozzles eject increasingly higher pressure water streams to promoteentangling in the intermediate layer to back layer of the laminate web,thereby achieving highly efficient production of a hydroentanglednonwoven fabric without disarray of fibers. Any of a low pressure method(20 to 55 kg/cm²), an intermediate pressure method (55 to 90 kg/cm²), ora high pressure method (90 to 200 kg/cm²) is arbitrary selecteddepending on the material, shape and basis weight of used webs and thenumber of treatment.

Although the shape of the high pressure fluid is not limited, columnarstreams are preferable in view of the energy efficiency. The crosssectional shape of the columnar stream is defined by the cross sectionalshape or internal structure of the small diameter nozzle and it can beselected depending on the material, object and uses of the web.

The processing speed of the hydroentangling step ranges from 2 to 200m/min. preferably 50 to 150 m/min. If the processing speed is lower than2 m/min, the productivity is low. On the other hand, if the processingspeed is higher than 200 m/min, sufficient entangling effect cannot beattained, which is not desirable.

Finally, the laminate composed of fiber web and reinforcing support basewhich was subjected to the high pressure hydroentangling is then passedthrough a drying process, wherein the laminate is dried up using, forexample, and oven 8, or a hot air oven, a heated cylinder or the likeand it is wound on a roll as a soft, lightweight reinforcedhydroentangled nonwoven fabric in the subsequent product takeup step.

The present invention will be further described with reference to thefollowing examples and comparative examples.

EXAMPLE 1, COMPARATIVE EXAMPLE 1

Rayon short fiber material of 2 denier in fineness, 50 mm in length and20 g/m² in average basis weight were made into a web (W₁) bycard-parallel method wherein fibers were oriented into two-dimensionalarrangement.

Polyethylene terephthalate (PET) resin (trademark: "MA 2100" made byUnitika Ltd.) was used as a raw material. The resin was spun from aspinneret to form melt-spun filaments and the filaments were arrangedlongitudinally with applying rotating hot air and collected on areticular endless belt conveyer, thereby obtaining a long fiber nonwovenfabric composed of longitudinally arranged unstretched filaments of 2denier in fineness. This nonwoven fabric was longitudinally stretched ata stretching ratio of 10 to make the fineness of fibers 0.2 denier bymeans of short distance roll stretching and further it was subjected totemporary bonding with polyvinyl alcohol, thereby obtaining alongitudinally stretched unidirectionally arranged nonwoven fabric (A₁)having a basis weight of 8 g/m².

Meanwhile, the same resin was spun likewise to form a long fibernonwoven fabric of transversely arranged fibers. It was transverselystretched at a stretching ratio of 10 and the fineness of fibers wasmade 0.2 denier through a pulley type transverse stretching method.Further it was subjected to temporary bonding with polyvinyl alcohol toobtain a transversely stretched unidirectionally arranged long fibernonwoven fabric (B₁) having a basis weight of 8 g/m².

A stretched cross-laminated nonwoven fabric (C₁) having a basis weightof 15 g/m² was prepared by laying down laminating the nonwoven fabric(A₁) with the nonwoven fabric (B₁) as the axial directions of thefabrics were crossed and by bonding temporarily using polyvinyl alcohol.Meanwhile, a stretched cross-laminated nonwoven fabric (D₁) having abasis weight of 14 g/m² was prepared by laying down laminating anonwoven fabric (A₁) with a nonwoven fabric (B₁) and it was subjected tothermal embossing process. These nonwoven fabrics were used asreinforcing support bases.

Laminates of web layers and a reinforcing support base having layerstructures of W₁ /A₁ /W₁, W₁ /B₁ /W₁, W₁ /B₁ /B₁ /W₁, W₁ /C₁ /W₁ and W₁/D₁ /W₁ were prepared. Each laminate was supplied on an endless beltconveyer of water permeable screen composed of a wire netting of 100mesh and it was then passed under three rows of small diameter nozzlesof 0.15 mm in orifice diameter with 1.0 mm pitch, wherein high pressurewater jet streams of 70 kg/cm² were applied in the first row of nozzles,90 kg/cm² water jet streams in the second row of nozzles and 110 kg/cm²water jet streams in the third row of nozzles, respectively. Thehydroentangling was carried out once from the upper side of the laminateand once from the reversed side at a processing speed of 100 m/min.After this entangling treatment, the laminate was dried to obtain athin, lightweight reinforced hydroentangled nonwoven fabric.

As Comparative Examples 1, a card web (W₁) made of rayon fiber havingthe same basis weight was subjected to the hydroentangling treatmentwith the same conditions.

Properties of the nonwoven fabrics produced in these examples are shownin Table 1.

                  TABLE 1                                                         ______________________________________                                                                   Tensile                                                              Basis    Strength  Elongation                                       Layer     Weight   (Lng/Trns)                                                                              (Lng/Trns)                               Example Structure (g/m.sup.2)                                                                            (kg/3 cm width)                                                                         (%)                                      ______________________________________                                        Example W.sub.1 /A.sub.1 /W.sub.1                                                               44       4.8/0.3    5/7                                     1       W.sub.1 /B.sub.1 /W.sub.1                                                               45       4.5/4.9   18/8                                             W.sub.1 /B.sub.1 /B.sub.1 W.sub.1                                                       51       5.1/8.3   20/9                                             W.sub.1 /C.sub.1 /W.sub.1                                                               54       8.7/5.8   22/5                                             W.sub.1 /D.sub.1 /W.sub.1                                                               51       6.9/5.5   10/7                                     Comp.   W.sub.1   50        0.4/<0.1  8/5                                     Exam. 1                                                                       ______________________________________                                         Note: (Lng/Trns) = Longitudinal/Transverse                               

EXAMPLE 2, COMPARATIVE EXAMPLE 2

Short fiber material made of polypropylene (trademark: "Nissaki PolyproJ 120" made by Nippon Petrochemicals Co., Ltd.) having fineness of 2denier, length of 50 mm and basis weight of 20 g/m², was formed into aweb (W₂) by two-dimensionally arranging through card-parallel method.

Polypropylene resin having density of 0.9 g/cm³ and melt flow rate of700 g/10 min as a raw material, was spun into a long fiber nonwovenfabric composed of longitudinally arranged unstretched filaments havingfineness of 2 denier through a process in the like manner as inExample 1. Then, the fineness of this nonwoven fabric was reduced to 0.2denier by longitudinally stretching in the like manner as in Example 1and it was subjected to temporary adhesion with polyvinyl alcohol toobtain a longitudinally stretched unidirectionally arranged long fibernonwoven fabric (A₂) of 6 g/m² in basis weight. Furthermore, thefineness of the same raw material as above was reduced to 0.2 denier bytransversely stretching in the like manner as in Example 1 and it wassubjected to temporary adhesion with polyvinyl alcohol to obtain atransversely arranged long fiber nonwoven fabric (B₂) of 6 g/m² in basisweight.

A stretched cross-laminated nonwoven fabric (C₂) having a basis weightof 11 g/m² was prepared by laying down the nonwoven fabric (A₂) with thenonwoven fabric (B₂) as the axial directions of the fabrics were crossedand by bonding them temporarily with polyvinyl alcohol. A stretchedcross-laminated nonwoven fabric (D₂) having a basis weight of 10 g/m²was prepared by laying down the nonwoven fabric (A₂) with the nonwovenfabric (B₂) and by bonding them temporarily with polyvinyl alcohol.These nonwoven fabrics were used as reinforcing support bases.

The reinforcing support bases were delivered to the collecting sectionof a card parallel web forming process and they were laminated into thelayer structures of W₂ /A₂ /W₂, W₂ /B₂ /W₂, W₂ /B₂ /B₂ /W₂, W₂ /C₂ /W₂and W₂ /D₂ /W₂. Then they were supplied on an endless belt conveyercomposed of water permeable screen of 100 mesh wire net, meanwhile, highpressure water jet streams were applied to the surface of each laminatefrom the upper side with three rows of nozzles, each of which wascomposed of a large number of small diameter nozzles, spaced at 1.0 mmpitch, the orifice diameter of 0.15 mm. The pressure of high pressurewater jet streams in the first row was 70 kg/cm², in the second row, 90kg/cm² and the third row, 110 kg/cm², respectively. The hydroentanglingtreatment was performed once from the upper side of a laminate and thenonce from the reversed side at a processing speed of 100 m/min. Afterthe entangling treatment, each laminate was dried, thereby obtainingthin, lightweight reinforced hydroentangled nonwoven fabrics.

In Comparative Example 2, only a card web (W₂) made of polypropylenefiber having almost the same basis weight as in the above-describedExamples were subjected to hydroentangling treatment under the sameconditions.

Properties of them are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                                   Tensile                                                              Basis    Strength  Elongation                                      Layer      Weight   (Lng/Trns)                                                                              (Lng/Trns)                               Example                                                                              Structure  (g/m.sup.2)                                                                            (kg/3 cm width)                                                                         (%)                                      ______________________________________                                        Example                                                                              W.sub.2 /A.sub.2 /W.sub.2                                                                45       4.7/0.3    5/8                                     2      W.sub.2 /B.sub.2 /W.sub.2                                                                44       4.7/4.4   61/7                                            W.sub.2 /B.sub.2 /W.sub.2 W.sub.2                                                        50       5.0/7.7   57/6                                            W.sub.2 /C.sub.2 /W.sub.2                                                                51       5.9/5.2   11/7                                            W.sub.2 /D.sub.2 /W.sub.2                                                                50       5.7/5.6   10/4                                     Comp.  W.sub.2    40        0.1/<0.1 12/5                                     Exam. 2                                                                       ______________________________________                                    

EXAMPLE 3, COMPARATIVE EXAMPLE 3

The reinforcing support bases (A₁) and (B₁) which were used in Example 1were fed to the web receiving section of a stretchable melt-blownnonwoven fabric (W₃), made by Kanebo Ltd., trademark: "Esupansione",made of polyurethane fiber. They were laminated together to form layerstructures of W₃ /A₁ and W₃ /B₁. Then these laminates were fed to anendless belt conveyer of water permeable wire net screen of 100 mesh,then high pressure water jet streams were applied to the laminates fromthe upper side through three rows of nozzles, each row of which wascomposed of a large number of small diameter nozzles, with 1.0 mm pitchand with orifice diameter of 0.15 mm. The pressure of high pressurewater jet streams in the first row was 70 kg/cm², the second row, 90kg/cm² and the third row, 110 kg/cm², respectively. The hydroentanglingtreatment was performed once from the upper surface the laminate andagain once from the reversed side at a processing speed of 100 m/min.After entangling treatment, the laminates were dried to obtain thin,light-weight reinforced hydroentangled nonwoven fabrics.

In Comparative Examples 3, only a melt-blown nonwoven fabric (W₃) madeof stretchable polyurethane which was used in this Example was subjectedto hydroentangling treatment under the same conditions.

Properties of them are shown in table 3.

                  TABLE 3                                                         ______________________________________                                                                  Tensile                                                              Basis    Strength   Elongation                                      Layer     Weight   (Lng/Trns) (Lng/Trns)                               Example                                                                              Structure (g/m.sup.2)                                                                            (kg/3 cm width)                                                                          (%)                                      ______________________________________                                        Example                                                                              W.sub.3 /A.sub.1                                                                        22       3.1/0.2      6/320                                  3      W.sub.3 /B.sub.1                                                                        21       0.3/3.4    380/7                                    Comp.  W.sub.3   15       0.3/0.2     380/400                                 Exam. 3                                                                       ______________________________________                                    

EXAMPLE 4, COMPARATIVE EXAMPLE 4

Nylon short fiber material of 2 denier in fineness and 50 mm in lengthwas made into a web (W₄) having a basis weight of 25 g/m² withtwo-dimensionally arranging by card parallel method.

Using polypropylene resin as a raw material, a longitudinally stretchedunidirectionally arranged long fiber nonwoven fabric (A₂) and atransversely stretched unidirectionally arranged long fiber nonwovenfabric (B₂) was prepared in the like manner as in Example 2. Then, astretched cross-laminated nonwoven fabric (C₄) having a basis weight of13 g/m² was prepared by laminating the nonwoven fabric (A₂) with thenonwoven fabric (B₂) as the axial directions of the fabrics were crossedand by bonding them temporarily with polyvinyl alcohol. Furthermore, astretched cross-laminated nonwoven fabric (D₄) having a basis weight of12 g/m² was prepared by laminating the nonwoven fabric (A₂) and thenonwoven fabric (B₂) as the axial directions of the fabrics were crossedand by applying thermal emboss treatment. These nonwoven fabrics wereused as reinforcing support bases.

The webs and reinforcing support bases were laminated to form layerstructures of C₄ /W₄ /C₄ and D₄ /W₄ /D₄, and the thus obtained laminateswere fed to a water permeable wire net screen of endless belt conveyerof 100 mesh. Then high pressure water jet streams were applied to thelaminates from the upper side through three rows of nozzles, each row ofwhich was composed of a large number of small diameter nozzles, with 1.0mm pitch and with orifice diameter of 0.15 mm. The pressure of highpressure water jet streams in the first row was 70 kg/cm², the secondrow, 90 kg/cm² and the third row, 110 kg/cm², respectively. Thehydroentangling treatment was performed once from the upper surface thelaminate and again once from the reversed side at a processing speed of100 m/min. After the entangling treatment, the laminates were dried toobtain thin, light-weight reinforced hydroentangled nonwoven fabrics.

In Comparative Examples 4, only a melt-blown nonwoven fabric (W₄) madeof nylon which was used in the above Example was subjected tohydroentangling treatment under the same conditions.

Properties of them are shown in table 3.

                  TABLE 4                                                         ______________________________________                                                                  Tensile                                                              Basis    strength   Elongation                                      Layer     Weight   (Lng/Trns) (Lng/Trns)                               Example                                                                              Structure (g/m.sup.2)                                                                            (kg/3 cm width)                                                                          (%)                                      ______________________________________                                        Example                                                                              C.sub.4 /W.sub.4 /C.sub.4                                                               49       6.5/7.0    6/8                                      4      D.sub.4 /W.sub.4 /D.sub.4                                                               49       7.9/8.3    8/9                                      Comp.  W.sub.4   50       0.8/0.1    15/5                                     Exam. 4                                                                       ______________________________________                                    

EXAMPLE 5

Using the same polyethylene terephthalate (PET) resin as the one used inExample 1 as a raw material, a long fiber nonwoven fabric composed oflongitudinally arranged unstretched filaments of 2 denier in finenesswas obtained by longitudinally arranging filaments spun from a spinneretwhile providing them rotating action by means of hot air and collectingthem on a circulating reticular endless belt conveyer. Then, alongitudinally stretched unidirectionally arranged long fiber nonwovenfabric (A₅) with basis weight of 7 g/m² and fineness of 0.2 denier wasobtained by subjecting the long fiber nonwoven fabric to short distanceroll stretching at a stretching ratio of 10.

Using the same resin and the same spinning method, a long fiber nonwovenfabric having transversely arranged fibers is formed, and a transverselystretched unidirectionally arranged long fiber nonwoven fabric (B₅) withbasis weight of 7 g/m² and fineness of 0.2 denier was obtained bysubjecting them to transverse stretching with a stretching ratio of 10by pulley type transverse stretching method.

A stretched cross-laminated nonwoven fabric (C₅) having basis weight of15 g/m² was prepared by laminating both the nonwoven fabrics together asthe axial directions of the fabrics were crossed and by bonding themtemporarily with polyvinyl alcohol. This stretched cross-laminatednonwoven fabric (C₅) was delivered on the endless belt conveyer of waterpermeable screen made of 100 mesh wire net. Then high pressure water jetstreams were applied to the surface of the laminate from the upper sidethrough three rows of nozzles, each of which row was composed of a largenumber of small diameter nozzles, spaced at 1.0 mm pitch with orificediameter of 0.15 mm, wherein the first row of nozzles gave high pressurewater streams at a pressure of 70 kg/cm², second row nozzles, 90 kg/cm²and the third row nozzles, 110 kg/cm², respectively. The hydroentanglingtreatment was carried out once to the upper side of the laminate andthen to the reversed side at a processing speed of 100 m/min. After theentangling treatment, the laminates were dried and a hydroentangled longfiber nonwoven fabrics (a) was obtained. The properties of the nonwovenfabrics are shown in Table 5.

The determination of lint-freeness was carried out according to "5.5.2Method for Measuring Flocking Strength, 1.5 R Method" of JIS L 1084(Test Standard for Flock Finished Cloth). In the method, the surface ofa test piece was scrubbed and the degree of fluff formed on the surfacewas observed by naked eyes. In the test, a test piece of 2×6 cm wasattached to a scrubbing rod of 1.5 mm in radius of curvature and anabrading cloth (cotton "Shirting No. 3" in JIS L 0803) was scrubbed 100times with a total load of 400 g at a rate of 30 reciprocations perminute. When flocking was less, it was judged as good, while theflocking was much, not good.

EXAMPLE 6

Polypropylene resin (density: 0.9 g/cm³, melt flow rate: 700 g/10 min)as a raw material was spun in like manner as in Example 5 and a longfiber nonwoven fabric composed of longitudinally arranged unstretchedfilaments of 2 denier in fineness was obtained. Then, a longitudinallystretched unidirectionally arranged long fiber nonwoven fabric (A₆) withbasis weight of 5 g/m² and fineness of 0.2 denier was prepared bysubjecting the above nonwoven fabric to short distance roll stretchingin the machine direction with a stretching ratio of 10.

The same thermoplastic resin was spun likewise to prepare a transverselyarranged long fiber nonwoven fabric was formed and a transverselystretched unidirectionally arranged long fiber nonwoven fabric (B₆) withbasis weight of 5 g/m² and fineness of 0.2 denier was prepared bysubjecting it to pulley type transverse stretching with a stretchingratio of 10.

A stretched cross-laminated nonwoven fabric (C₆) having basis weight of10 g/m² was prepared by laminating both the nonwoven fabrics as theaxial directions of the fabrics were crossed on the line just after thestretching step of the nonwoven fabric A₆.

This stretched cross-laminated nonwoven fabric (C₆) was delivered on theendless belt conveyer of water permeable wire net screen of 100 mesh.The high pressure water jet streams were applied to the surface of thelaminate from upper side through three rows of nozzles, each of whichrows is composed of a large number of small diameter nozzles, spaced at1.0 mm pitch, with orifice diameter of 0.15 mm, wherein the first rownozzles ejected high pressure water jet streams at a pressure of 70kg/cm², the second row nozzles, 90 kg/cm² and the third row nozzles 110kg/cm², respectively. The hydroentangling treatment was performed onceon the upper side of the laminate and then on the reversed side at aprocessing speed of 10 m/min. After the entangling treatment, thelaminates were dried to obtain a hydroentangled long fiber nonwovenfabrics (b) was obtained. Properties of them are shown in table 6.

EXAMPLE 7

A nonwoven fabric having a layer structure of A₅ /B₅ /B₅ /A₅ with abasis weight of 32 g/m² was prepared by laminating a longitudinallystretched unidirectionally arranged long fiber nonwoven fabric (A₅) anda transversely stretched unidirectionally arranged long fiber nonwovenfabric (B₅) as prepared in Example 5 and the laminate was thentemporarily bonded with polyvinyl alcohol. This nonwoven fabric wasdelivered on the endless belt conveyer composed of water permeablescreen of 100 mesh wire net. The high pressure water jet streams werethen applied to the surface of the laminate from upper side throughthree rows of nozzles, each of which rows was composed of a large numberof small diameter nozzles, spaced at 1.0 mm pitch, with orifice diameterof 0.15 mm, wherein the first row nozzles ejected high pressure waterjet streams at a pressure of 70 kg/cm², the second row nozzles, 90kg/cm² and the third row nozzles, 110 kg/cm², respectively. Thehydroentangling treatment was performed once on the upper side of thelaminate and then on the reversed side at a processing speed of 10m/min. After the entangling treatment, the laminates were dried and ahydroentangled long fiber nonwoven fabric (c) was obtained. Itsproperties are shown in Table 5.

EXAMPLE 8

A long fiber bundles made of PET resin used in Example 5 was subjectedto stretching, crimping, fiber opening and spreading to obtain alongitudinally stretched unidirectionally arranged long fiber nonwovenfabric (A₇), in which the stretching ratio was 6.5, basis weight, 20g/m² and fineness, 0.3 denier. Then, a nonwoven fabric having basisweight of 27 g/m² was prepared by laminating the above nonwoven fabricwith a transversely stretched unidirectionally arranged long fibernonwoven fabric (B₅) used in Example 5 having a basis weight of 5 g/m²and fineness of 0.2 denier as the axial directions of the fabrics werecrossed, and by bonding them temporarily with polyvinyl alcohol.

This nonwoven fabric was delivered on the endless belt conveyer of waterpermeable screen composed of 100 mesh wire net, then the high pressurewater jet streams were applied to the surface of the laminate from upperside through three rows of nozzles, each of which rows comprising alarge number of small diameter nozzles, spaced at 1.0 mm pitch, withorifice diameter of 0.15 mm, wherein the first row nozzles ejected highpressure water jet streams at a pressure of 70 kg/cm², the second rownozzles, 90 kg/cm² and the third row nozzles, 110 kg/cm², respectively.The hydroentangling treatment was performed once on the upper side ofthe laminate and then on the reversed side at a processing speed of 10m/min. After the entangling treatment, the laminate was dried and ahydroentangled long fiber nonwoven fabric (d) was obtained. Theproperties of the nonwoven fabric are shown in Table 5.

COMPARATIVE EXAMPLE 5

Short fiber material made of PET of 2 denier in fineness, 50 mm in fiberlength and 40 g/m² in average basis weight was formed into a nonwovenfabric by semi-random card process wherein fibers were arranged into anintermediate state between two-dimensional arrangement andthree-dimensional arrangement.

This nonwoven fabric was fed to the endless belt conveyer of waterpermeable screen composed of 100 mesh wire net. The high pressure waterjet streams were applied to the surface of the laminate from upper sidethrough three rows of nozzles, each of which rows comprising a largenumber of small diameter nozzles, spaced at 1.0 mm pitch, which orificediameter of 0.15 mm, wherein the first row ejected high pressure waterjet streams at a pressure of 70 kg/cm², the second row nozzles, 90kg/cm² and the third row nozzles 110 kg/cm², respectively. Thehydroentangling treatment was performed once on the upper side of thelaminate and then on the reversed side at a processing speed of 10m/min. After the entangling treatment, the laminate was dried and ahydroentangled short fiber nonwoven fabrics (e) having basis weight of34 g/m² was obtained. Their properties are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                                  Tensile Elonga-                                                       Basis   Strength                                                                              tion   Lint                                        Layer      Weight  (Lng/Trns)                                                                            (Lng/Trns)                                                                           Free-                                Example                                                                              Structure  (g/m.sup.2)                                                                           (kg/3 cm w.)                                                                          (%)    ness                                 ______________________________________                                        Exam. 5                                                                              (a)A.sub.5 /B.sub.5                                                                      14      2.5/2.3  9/11  Good                                 Exam. 5                                                                              (b)A.sub.6 /B.sub.6                                                                      10      1.7/1.8 7/8    Good                                 Exam. 5                                                                              (c)A.sub.5 /B.sub.5 /B.sub.5 /A.sub.5                                                    28      5.8/5.9 10/12  Good                                 Exam. 5                                                                              (d)A.sub.7 /B.sub.5                                                                      25      2.8/2.4 45/7   Good                                 Comp.  (d)        34      3.4/1.6 45/98  No                                   Exam. 5                                  Good                                 ______________________________________                                    

INDUSTRIAL APPLICABILITY

The thin, lightweight reinforced hydroentangled nonwoven fabrics of thisinvention posses excellent properties in high mechanical strength whichhas not been achieved with any prior art hydroentangled nonwovenfabrics, despite the nonwoven fabric of the invention are thin andlightweight because they are strengthened by a reinforcing support basescomprising stretched nonwoven fabrics produced by unidirectionallystretching long fiber nonwoven fabrics having unidirectionally arrangedfibers or nonwoven fabrics formed by crosswise laying down the stretchednonwoven fabrics.

In addition, it is possible to impart to final products any desiredbalance in mechanical strengths between longitudinal direction andtransverse direction adapted to their uses by selecting adequatereinforcing support base from nonwoven fabrics having high mechanicalstrength in the longitudinal direction, nonwoven fabrics having highmechanical strength in the transverse direction, or nonwoven fabricshaving balanced mechanical strength both in longitudinal and transversedirections.

The thin, lightweight reinforced hydroentangled nonwoven fabricsprepared in accordance with the present invention have improved tensilestrength, peel strength, soft touch feeling, drape and uniformity ofnonwoven fabric. Moreover, the balance of mechanical strengths betweenlongitudinal direction and transverse direction can be freely designedin compliance with their uses. The method of the present invention iseconomical without losing the high-speed productivity which is inherentin the web forming process and hydroentangling process. Accordingly, theproduct according to the present invention can be used widely forapparel materials such as interlining in which the reinforcing functionand elongation and direction controlling functions are required,industrial materials such as filters and wiping cloth, disposablemedical supplies such as operating gowns, bed sheets, towels and masks.

What is claimed is:
 1. A hydroentangled nonwoven fabric produced by thesteps which comprise spinning a thermoplastic resin into a long nonwovenfabric and entangling at least one layer of stretched unidirectionallyoriented nonwoven fabric or a stretched cross-laid down and/or laminatednonwoven fabric made by crosswise laying down and/or laminating saidstretched unidirectionally oriented nonwoven fabric with high pressurewater jet streams, said stretched unidirectionally oriented nonwovenfabric being made by unidirectionally stretching said long fibernonwoven fabric and orienting its fibers almost in one direction.
 2. Ahydroentangled nonwoven fabric as claimed in claim 1, wherein saidhydroentangled nonwoven fabric is produced by laying down or laminatingsaid stretched unidirectionally oriented nonwoven fabric or saidstretched cross-laid down and/or laminated nonwoven fabric with anoptional fiber web and then entangling with high pressure water jetstreams.
 3. A hydroentangled nonwoven fabric as claimed in claim 2,wherein said fiber web is any one of a card web made of natural fiber,regenerated fiber or synthetic fiber.
 4. A hydroentangled nonwovenfabric as claimed in claim 2, wherein said fiber web is a long fibernonwoven fabric before the stretching of said stretched unidirectionallyoriented nonwoven fabric, a stretched randomly oriented nonwoven fabric,a non-stretched randomly oriented or unidirectionally oriented nonwovenfabric or a fiber web consisting of natural fiber, regenerated fiber ofsynthetic fiber.
 5. A hydroentangled nonwoven fabric as claimed in anyof claims 1 to 4, wherein said stretched unidirectionally orientednonwoven fabric has a stretching ratio of 5 to 20, an average finenessof 0.01 to 10 denier and a basis weight of 1 to 80 g/m².
 6. A method forproducing hydroentangled nonwoven fabric comprising the steps ofspinning a long fiber nonwoven fabric from a thermoplastic resin,unidirectionally stretching said nonwoven fabric to form a stretchedunidirectionally oriented nonwoven fabric having fibers oriented almostin one direction, feeding said stretched unidirectionally orientednonwoven fabric or a stretched cross-laid down and/or laminated nonwovenfabric made by laying down and/or laminating said stretchedunidirectionally oriented nonwoven fabric, and entangling said fedmaterials by high pressure water jet streams of 10 to 300 kg/cm² at aprocessing rate of 2 to 200 m/min.
 7. A method for producinghydroentangled nonwoven fabric as claimed in claim 6 wherein saidstretched unidirectionally oriented nonwoven fabric or said stretchedcross-laid down and/or laminated nonwoven fabric is laid down with anoptional fiber web and then high pressure water jet streams of 10 to 300kg/cm² at a processing rate of 2 to 200 m/min are applied to entanglesaid materials together.
 8. A method for producing hydroentanglednonwoven fabric as claimed in claim 6 or 7 in which said stretchedunidirectionally oriented nonwoven fabric has a stretching ratio of 5 to20, an average fineness of 0.01 to 10 denier and a basis weight of 1 to80 g/m².